1. Field of the Invention
The present invention is concerned with a method of manufacturing and loading of so-called tubular bags under sterile conditions; in particular, it relates to pre-sterilizing a tubular bag packaging machine of the afore-mentioned type, with sterile conditions of the said machine, after pre-sterilization, being maintained.
2. Description of the State of Art
Following the pre-sterilization step presently of interest, during permanent operation of a machine of the afore-described type, at least one longitudinally sealed tubular strip is formed from a web of packing material supplied in timed sequence from a magazine roll, moving past a sterilizing station. A tubular strip of the afore-described type is then cross-sealed underneath the forming and loading station; the material to be loaded is filled via a metering device through a forming and filling pipe forming an integral part of the machine, into the end of the tube closed at the bottom, withdrawn by a package length and again cross-sealed to form a closed and filled bag pack which is then cut from the subsequent strip, etc. The advance of the web of packing material withdrawn from the magazine roll is within a sterile chamber equally pre-sterilized and under an excess sterile air pressure.
The afore-described method of manufacturing and loading tubular bags under sterile conditions has been described, for example, in German Patent Application DE 199 10 485 A1, requiring, prior to commencement of the repeat permanent operation, a pre-sterilization of the sterile space, of the metering device metering the material to be loaded, and of the forming and loading station located in the end area of the sterile space and consisting of one or more forming and filling pipes. To the extent as known in the art, integrated into the said pre-sterilization process is the tube of packing material formed by longitudinal sealing into a tube and cross-sealed by cross-sealing jaws arranged externally of the sterile chamber thereby enabling the tube to be withdrawn. In order to incorporate, during pre-sterilization, the packing material-sided face of the shaping pipe, on the one hand, and to insure, on the other hand, the discharge of the sterilizing agent, it is imperative for the forming and loading station to be provided not only with a forming pipe but also with a filling pipe disposed concentrically within the forming pipe in order to thereby enable an adequate discharge of the sterilizing agent through an annular gap formed thereby. Concerning dual tubes of this type, reference is made, for example, to European Patent Application EP-A-0 232 943; German Patent Application DE-A-195 10 555 A1 and to U.S. Pat. No. 4,537,007. According to the two former-mentioned literature references special means, such as adjustable dual valves or separately removable closure caps, are additionally provided in order to apply, internally and externally, sterilizing agent to the pipes, with the sterilization being restricted to the loading material-sided face of the packing material. In the packaging machine according to U.S. Pat. No. 4,537,007, the packing material first moving through a sterilizing bath, will pass two sterile chambers separated from one another in order to be steam-dried in the first chamber and to be loaded in the second chamber after cross-sealing having been effected therebelow or outside thereof. The packaging machine according to the afore-mentioned DE-A-199 10 458 A1 also operates on dual pipes of this type, i.e. on a loading pipe concentrically arranged within the forming pipe. In addition, it should be noted that in one form of embodiment of the afore-going machine the dual tube, for pre-sterilizing purposes, is required to be withdrawn from the tube already formed.
The present invention proceeds from the said DE-A-199 10 485 A1 because the basic principle thereof, i.e. withdrawing the web of packing material from a magazine roll and moving the same past a packing web sterilizing station, with a single sterile chamber attached thereto for sterilizing a web of packing material, wherein the forming and loading station is integrated into the end region of the sterile chamber, has proved successful.
Referring to the afore-described verified state of art, the problem underlying the invention and the object of the invention, respectively, reside in simplifying the required pre-sterilizing method for packing or tubular bag-manufacturing and filling machines of this type and in improving the machine itself to the effect that only one pipe is required per bag strip, i.e. one pipe serving as a forming pipe and at the same time as a loading pipe with no valve required and the arrangement being stationary.
This problem, in the practice of the invention, for pre-sterilizing a tubular bag packaging machine of the afore-mentioned type, has been solved by the following pre-sterilizing steps:
1.1 sterilizing the device metering the material to be loaded by saturated steam;
1.2 after termination of the supply of steam, supplying sterile air to the meter and to the sterile chamber, maintaining the supply of sterile air during subsequent steps;
1.3 withdrawing the web of packing material from the magazine roll through the sterile chamber partially kept open for withdrawing the web while forming tubes down to underneath the forming station;
1.4 closing the sterile chamber and supplying a mix of sterile agent and steam to the sterile chamber, with the tube of packing material kept open or being opened at the bottom;
1.5 after completion of the sterilizing phase by the mix of sterile agent and steam, the sterile chamber and all elements contained therein are dried by the flow of sterile air maintained;
1.6 after drying, the supply of sterile air to the meter is discontinued while the supply thereof to the sterile chamber is maintained;
1.7 subsequently, the tube end formed by cross-sealing and respectively withdrawn by the length of a bag is loaded via the metering device.
What is essential and crucial of the invention is that the tubular web of packing material behind the outlet from the sterile chamber and the permanent supply of sterile air thereto be specifically kept open or be opened; in this connection it should be noted that the alternative statements xe2x80x9ckept open or be openedxe2x80x9d convey that, on the one hand, the provision of the machine with a new magazine roll and, on the other hand, an interruption of the permanent operation of the machine have been taken into account; in the latter instance, the tube having a cross-sealing, underneath the outlet, suspends from the sterile chamber.
When re-furnishing the machine with a web of packing material, threading thereof into the machine and forming thereof on the forming pipe, the tube formed on the forming pipe by longitudinal sealing is withdrawn by the cross-sealing jaws; however, the latter have not been heated yet nor do they have reached the sealing temperature with the result that no cross-sealing takes place, i.e. the tube after resetting of the cross-sealing jaws, will remain open and not kept in tight abutment with the forming pipe, which is a requirement for enabling the supplied mix of sterile agent and steam (or steam as a carrier for hydrogen peroxide) to enter the gap between packing material and forming pipe, to flow therethrough and get discharged by simply flowing off downwardly through the open-ended tube. Alternatively, a gap between tube and forming pipe can be formed otherwise, if need be, by way of addition, yet to be described hereinafter.
However, the same effect results in the second instance, i.e. in the event of an interruption of operation which requires, as a rule, a renewed pre-sterilization and, in the majority of interruptions, will be overcome by re-threading the web of packing material. Otherwise, the already cross-sealed end of the tube will be pointedly cut off (optionally, in case of an interruption of the supply of filling material, after producing a number of empty bags), thereby, again, forming an open end of the tube. Apart from another measure yet to be explained in this context, the cross-sealing and withdrawing jaws of the machine, for cutting purposes, at the side of the outlet opening can be provided with a cutter; in this respect it is expressly pointed out that said cutter has nothing in common with the cutting elements provided, as a rule, centrally across the entire bag width within the cross-sealing jaws to thereby separate, in timed sequence, a filled bag from the following strip.
As a cut to open the tube as described hereinbefore, optionally, can also manually be carried out by means of scissors, such an additional cutter, admittedly, is of advantage but not imperative, i.e. basically, no changes are required in a conventional packaging machine of the afore-mentioned type for manufacturing and filling tubular bags to carry out the process of the invention, except for corresponding control means. However, it is of additional advantage that for forming the tube and for supplying the filling material, one tube is adequate as it normally is in non-aseptically operating packaging machines for tubular bags.
At this point, it should be noted that so far, reference has been made to one tube only; it goes without saying that the process of the invention also can be carried out on tubular bag packaging machines that are provided with forming tubes arranged in series and in side-by-side relationship, wherein webs of packing material are processed that are cut into correspondingly thin strips. The same applies to machines for manufacturing so-called three-edge sealing bags wherein a web of packing material of corresponding width is placed about two relatively narrow-spaced tubes, with the longitudinal joint being provided between the tubes at the longitudinal web edges and the web.